1. Field of the Invention
The present invention relates to automatic or semi-automatic fastener insertion machines, and more particularly to a method and apparatus for automatically changing the upper and/or lower tools of a fastener insertion machine.
2. Description of the Prior Art
Fastener insertion machines are sometimes referred to as presses or hydraulic presses. These machines use very high pressure to permanently attach fasteners of different sizes and shapes to workpieces. In a typical fastener insertion machine, an upper tool and a lower tool are provided in vertical alignment. A flat surface on a workpiece is placed between the upper and lower tools of the machine. The workpiece is positioned either manually or automatically so that the appropriate location (usually a pre-cut opening) on the workpiece is placed between the machine tooling to receive the fastener. A fastener is delivered to the machine tooling, and the machine is then operated such that the upper and lower tooling are pressed firmly together causing the fastener to be attached to the workpiece. The tooling then retracts, allowing the workpiece to be moved or removed before the next insertion cycle.
Fastener insertion machines typically require that both the upper and lower tooling correspond to the particular fastener to be inserted. Fasteners of different sizes and shapes generally require different upper and lower tooling; the same tooling is generally not usable for more than one type of fastener. Once the upper and lower tooling is set, the insertion machine may be operated repetitively to insert hundreds or thousands of the same kind of fasteners into workpieces.
It is becoming increasingly more common for a single workpiece to require the insertion of more than one different kind of fastener. Using existing fastener insertion machines, this may be accomplished by passing a batch of workpieces through a single insertion machine several times, changing the tooling and the fastener to be inserted on each pass. This approach is inefficient, time consuming, and expensive because, among other things, the same batch of workpieces (potentially many thousands of them) must be accumulated and stored following each pass through the machine, pending the change to the next set of tooling/fastener for the next pass.
Alternatively, a different fastener insertion machine could be used to insert each different fastener on the workpiece. While such an assembly line of insertion machines would be more efficient than using a single machine, it is a much more expensive proposition. A better solution would be a single machine that is capable of automatically changing tooling so that many different kinds of fasteners could be inserted on a workpiece during a single pass of the workpiece through the machine.
There are a number of tool changing devices that have been developed for punch presses in the prior art. (E.g. U.S. Pat. Nos. 4,205,427; 4,719,691; 5,699,866.) Such devices generally include a magazine of alternative upper tools which can be swapped out using one of a variety of grippers. However, since these machines have been developed for punch presses which generally cut holes into workpieces, they generally deal with changing only the upper cutting tool. Other tool changing devices such as those described in U.S. Pat. Nos. 3,811,179; 4,696,091 and 5,762,594 describe similar devices which are also designed to only change the upper tools using a magazine of available tools. U.S. Pat. No. 5,326,201 describes a complicated mechanism for changing upper tools in a blind broaching machine. However, neither this nor any of the above listed inventions make any provision for changing the lower tooling. U.S. Pat. No. 4,269,739 describes a tool changing device for a turret punch press which includes changing the lower tooling; however, the turret operation of this device is highly specific, and differs greatly from the present invention. None of the above inventions make any provision for supplying fasteners to the tooling, holding the different fasteners associated with different tooling, or changing to a different fastener supply with the change in tooling.